Process of dyeing



water in their oxidized Patented Nov. 12, 1935 UNITED STATE-S PATENT, OFFICE z,ozo.4ss raocsss or DYEING No Drawing. Application May is, 192.2, SerialNo. 611,753

15 Claims.

The present invention relates to improvements in the art or sulphur, carbazole and vat dyeing processes. As is well known to those skilled in the art, the foregoing dyestuffs are insoluble in state, but are soluble in their leuco form. In order to render these dyestufis soluble in water, they are reduced in a strongly alkaline solution. Thus, the sulphur and carbazole dyestufis are ordinarily obtained in solution by reducing them with NaaS' in a concentrated solution of soda ash, while the vat dyes are rendered soluble by reducing the same with sodium hydrosulphite in a concentrated solution of NaOH. Some of the carbazole dyestuffs are not reducible and rendered soluble by reduction with sodium sulphide in the presence of Nazcoa, but must be solubilized by reduction with NaOH and sodium hydrosulphite. Broadly speaking, sulphur and carbazole dyes are vat dyestuffs, because they are insoluble in water, but may be solubilized by alkaline reduction. However, the practical dyer considers sulphur dyes to be those water insoluble dyes which are solubilized by reduction with sodium sulphide in a hot concentrated solution of sodium carbonate. and which dye cotton, usually at the boil. Vat dyes on the other hand, are considered by the practical dyer, to be those dyestufis which are solubilized by reduction with sodium hydrosulphite in a rather concentrated solution of sodium hydroxide. And intermediate between these two extremes, lie the carbazole dyes, some of which maybe solubilized in the same manner as sulphur dyes, and others requiring the more energetic reduction provided for in the case of what the practical dyer considers a vat dye.

One of the major difliculties in the application of sulphur, carbazole or vat dyestuffs to the fibrous material is premature oxidation. This difliculty is particularly troublesome in the vat dyeing of piece goods in a dyeing jigger, because when cotton piece goods are dyed in a jigger with a vat dye, the selvedges of the goods which are more accessible to the atmosphere than the central portion of the piece goods, are oxidized by the oxygen of the air with theresult that the piece is side-shaded", or in other words, the sides of the piece are deeper or fuller in shade than the central portion. Of course such a result is highly unsatisfactory. The mode of procedure in jigger dyeing is such that it is very difllcult to prevent this side-shading, since the operation is slow and any given portion of the cloth is immersed in the dye bath for a comparatively short period of time. For example,

let us assume that 1,000 yards of cotton about 36 inches wide and weighing about pound per yard is to be dyed a khaki shade with ind-' anthrene dyestufis. The depth of the shade together with the weight of the piece goods will 5 require that the dye liquor contain several pounds of dyestuffs. In order to acquire the depth of shade necessary the dyeing operation proper (exclusive of oxidation and washing steps) will require about eight "ends or eight passages through 10 the dye liquor, each end consuming about ten minutes. The dyeing operation will consume, therefore, about one hour and twenty minutes, and it is .very difficult to keep the dyestufi in a. reduced state for this period\of time. It will be 15 found that edges of the roll of cloth being dyed will have become at least partially oxidized. In obtaining a khaki shade with indanthrene dyestuffs, indanthrene brown, olive and yellow are employed and the vat is a wine color. Now as 20 the dyeing operation proceeds, it will be observed that the edges of the roll will not be wine colored, but will be greenish yellow in color, indicating oxidation. To offset as much as possible the premature oxidation, sodium hydrosulphite is 25 added during the dyeing operation, usually at the end of a half hour.

Also, the addition of other types of reducing agents such as zinc-formaldehyde-sulfoxylate and the like has been proposed. The addition of 30 acetone to the dye liquor tends to stabilize sodium hydrosulphite solutions.

In order to prevent premature oxidation I employ a suitable amount of lecithin, such as might be obtained from soya beans, dispersed in aqueous 5 solution (for example the dye solution or dye liquors) by the aid of suitable emulsifiers or other colloidal media, such as the potassium and/or sodium salt of naphthenic acid, sodium and/or potassium salts of the fatty acids; or such as 40 suitable solvents as phenyl carbinol, butyl cellusolve and the like, or mixtures of any of these materials.

This mixture may be added to the dyestufl or to the paste before reduction or to the reduced solution or to the dye bath'proper, or at any other convenient point.

The correct amount to be used would depend on the type of dyeing apparatus and other con- 50 ditions. For instance, the open type machines (jiggers and the like) would require more than the closed type (closed kettles and the like), since the dye liquor comes in contact with more air, hence oxidation takes place to a greater extent.- 55

It varies between 0.5% and 3.0% of lecithin on the weight of material being treated.

In order to describe the invention more'completely, the following specific examples are given by way of illustration.

Imp: I

In preparing a dye bath containing Ciba brown R Colour Index No. 1187 concentrated powder, I first prepare a.paste containing 2,000 c. c. of NaOH solution of 86' 'I'waddell and 1,000 srams of the above dyestuif. When a uniform paste has been produced I introduce the same into 00 liters of water, maintained at a temperature of 70 C., continuously stirring the mixture. 1200 grams of sodium hydrosulphite are then slowly added and stirring is continued until reduction is complete, as indicated by the appearance of the brownish yellow colored vat. I then add 200 grams of soya bean lecithin containing 60% lecithin. The solution is cooled to 20/30 C., and diluted with twenty volumes of water to produce the final bath. The dyeing operation is carried out at 20/30' C.

Example I! In preparing a dye bath containing Cibanone red 48 Colour Index Supplement page 35, concentrated powder, I prepare a paste, containing 5,000 c. c. of NaOH solution of 65 'Iwaddell and 1,000 grams of the dyestufl. This paste is diluted with 100 liters of water maintained at. a temperature between 40 and 50 C. 7500 grams of sodium hydrosulphite are then added and the mixture is stirred until reduction is complete, as indicated by the appearance of the blue red colored vat. This reduced liquor may be diluted with twenty volumes of water. I then add 150 rams of soils. bean lecithin.

Example III A dye bath containing Cibanone black B may be prepared in the manner described in the preceding examples, using 1,000 grams of the dyestufi, 5,000 c. c. of 66 Twaddell NaOI-I solution, 150 liters of water and 2,000 grams of hydrosulphite, reduction taking place at 60 C. I may add 175 grams of lecithin to the paste or I may add it to the reduced vat, either before or after final dilution. The dye is applied to the fiber at a temperature lying between 60 and C.

It will be understood that in the above examples the amount of dyestufi used per given weight of cotton or other fibrous material will depend on the shade desired. These examples are very broad types and show a wide range of temperatures, proportions and so forth.

In carrying out the invention in connection with the sulphur dyestuif I may proceed as follows.

Example IV I first prepare a smooth paste containing 5,000 grams of Pyrogene deep black B Colour Index No. 991, in 20,000 grams of warm water. I then add 5,000 grams of crude sodium sulphide and 2,000 grams of soda ash. The mixture is thoroughly stirred while heating to C. I then add 500 grams of scya bean lecithin before final dilution of the dye liquor.

Example v I first prepare a smooth paste containing 5,000 grams Pyrogene brown 48 extra concentrated Colour Index No. 51, 20,000 grams of warm wa- Example VI l0 Ciba blue 2 RH page 84 of Supplement to Colour Index, 1 pound color, 10 gallons water, 2% pounds NaOI-I 76%, 1% pounds hydro, 2 ounces lecithin, reduce 160 F. dye at I"., reddish yellow reduction. 0 15 Example VII Ciba yellow G Colour Index No. 1196, 1- pound color, 10 gallons water, 2% pounds NaOH, 1% pounds hydro, 2%. ounces lecithin, reduce at 20 I". dye at 120 F., reddish violet reduction.

In .the foregoing examples, it will be observed that only one dyestufi has been used in preparing the bath. As a matter of fact a mixture of three or four dyestuffs are used in actual practice in 25 order to obtain a given shade. This fact is well known to the practical dyer and he can readily observe from the proportions of dyestui! and lecithin set forth above, the amount of lecithin that should be used with a given weight of dyestufi', that is the total weight of the mixture of dyestufis where such mixture is used. Also vat dyes usually are sold in the form of a 20% paste, by the manufacturer, and since the above proportions are based on the weight of dry powder, 35 the dyer must take this fact into consideration.

Certain types of dyestufi, for instance Ciba yellow G, extra concentrated Colour Index No. 1196, cannot be run as self shades except for tinting on the continuous dyeing machines (piece goods 40 or warps). In fact, practically all vat colors are limited to a medium shade on this particular machine. The reasons for this are that the fact the dyestuif in the high concentration necessary, would be prematurely oxidized. That, of course. 45 causes inferior dyeing results, such as specks of precipitated dyestuff, excess foam marks, unevenness of shade, and the fastness is not in keeping with that expected from this class of dyestuffs. In the present practice, Cibanone 50 blue G Colour Index No. 1195, is limited to concentrations of 5 ounces of dyestuif per gallon; Cibanone brown GR paste Colour Index No. 1173 is limited. to 16 ounces per gallon of liquor; Cibanone blue 36 double paste is limited to 55 3 ounces per gallon. With the aid of lecithin this concentration can be increased to a point where the operation is profitable, considering the increase in concentration of dyestufi' which is used, and the increase in the amount of color that a 60 givTaK quantity of dyestufi! will produce. At the same time, the reduction can be maintained over a suificlent period of time to allow the running of adequate yardage to make the operation profitable. For instance, Cibanone blue G double paste Colour Index No. 1115, 5 ounces per gallon will run not over eighty minutes after reduction, whereas with the aid of lecithin it will run approximately double that time, or minutes. 7

WhileI donotwishto limitmvselftoanyparo ticular theory, I am of the opinion that lecithin prevents premature oxidation by the mechanism of selective absorption of oxygenand also that the lecithin forms a protective shield, which pro- 75 paste or to the diluted mixture oi dy'estufl and reducer, either before or after reduction.

Having disclosed the nature of my invention,- what I'claim is:

1. A process for alkaline reducing agent which comprises preparing a reduced alkaline solution of the dyestufi containing lecithin,

and immersing the said fibrous material therein. 2. A process for dyeing fibrous material with a water insoluble dyestufi which may be dissolved in an alkaline reducing medium, which comprises adding a small quantity of lecithin to the dyestuff, adding the dyestufl to an alkaline reducing medium while stirring to facilitate reduction and immersing the said fibrous material I therein. I

3. A process for dyeing fibrous material with a vat dyestufi which comprises preparing a reduced alkaline solution of the said dyestufl containing a small quantity of lecithin and immersing the said fibrous material therein.

4. A process for dyeing fibrous material with a vat dyestufi which comprises reducing the said vat dyestufi in an alkaline reducing medium,

' adding a small quantity of lecithin and immersing the said fibrous material therein.

5. A processfer dyeing fibrous material with a sulphur dyestufi which comprises preparing a reduced alkaline solution of the said dyestufi containing a small quantity of lecithin and immersing the said fibrous material therein.-

6. A process for dyeing fibrous material with a sulphur dyestufl which comprises reducing thesaid sulphur dyestufi in 'analkaline reducing stage of the-dyeing process, that is it may be added-to the original v I I a carbazole dyestufi dyeing fibrous material with 2 reduced. alkaline solution of the-said dyestufi' con- 10 a dyestufi which is soluble only in an alkaline medium, and by virtue ofi an 3 medium, adding a small quantity of lecithin and immersing the said fibrous material therein.

7. A process for dyeing fibrous material with-a carbazole .dyestufl which comprises reducing the said carbazole dyestuff in an alkaline reducing 5 .medium, adding a smal quantity oflecithin and v immersing the said fibrous material therein.

8. A process for dyeing fibrous material with a which comprises preparing a 10. A- process for dyeing fibrous material witha water insoluble dyestufi which may be dissolved in an alkaline medium and by virtue of an alkaline reducing agent, which comprises preparing a reduced alkaline solution of the dyestufi containing a small amountof lecithin and immersing the said fibrous material therein.

11. A process for dyeing fibrous material with a water insoluble dyestufi which may be dissolved in an alkaline medium and by virtue of an alkaline reducing agent, which comprises preparing a reduced alkaline solution of the dyestufl containing a small amountof lecithin, at least 2.5% by weight of the dyestufl, and immersing the said fibrous material therein.

12. As a new composition of matter, a sulphur dye bath containing lecithin.

13. As a new composition of matter, a car: bazole dye bath containing lecithin. I

14. A newcomposition of matter for addition to an alkaline reducing bath comprising a vat. dye paste containing lecithin.

15. A new composition of matter for addition to an alkaline reducing bath, a dyestufl of the group consisting of 4 PAUL BoLEN- vat, sulphur and carbazole ,dyestuffs in powder form, containing lecithin. 40 

